1. Field of the Invention
The present invention relates to a receiving apparatus and a transmitting/receiving system which are capable of transmitting and/or receiving, between rooms spaced apart from each other, data outputted via an electric power line (outlet) from an electronic apparatus such as an audio unit, a video unit or a computer installed in a house for example.
2. Description of the Related Art
There is proposed a power-line communication system where data outputted from an electronic apparatus such as an audio unit, a video unit or a computer installed in a house for example are transmitted and received via an electric power line (outlet).
The above power-line communication system is adapted for transmitting various information signals via an electric power line as a transmission path furnished to supply commercial power therethrough. In this power-line communication system, an output signal to be sent is generated by converting, through a modem, a data set outputted from a personal computer or the like, and then the data set thus obtained is sent via an electric power line from an outlet. Also according to the power-line communication system, the output signal delivered to the power line is received via the outlet, and then the data set is demodulated. Thus, the power-line communication system is capable of transmitting various information signals with facility and simplicity by the use of an existing power line in a house or the like.
Since a variety of electric apparatus are mutually connected via the power line with outlets, various noises are generated from such electric apparatus, whereby extreme disturbance noises are caused in the power-line communication system.
In addition to connection of various electric apparatus to the power line via outlets, various kinds of wires are arranged in various forms at various positions, so that it is difficult to specify the characteristic impedance. Consequently, by applying to a power-line communication system, generation of a zero transmission point and a nonlinear phase characteristic is unavoidable due to the impedance mismatching. Thus, in the power-line communication system, there have been some disadvantages including that the signal level of a transmission signal inputted via an outlet is extremely lowered depending on the position where a receiving apparatus is connected to the power line, and further the signal level of the transmission signal is varied.
On account of the problems mentioned, it has been difficult heretofore in the power-line communication system to achieve exact transmission of an information signal with stability and certainty.
When stable and certain transmission of an information signal is difficult to achieve as described, it becomes eventually necessary to transmit the information signal at a lower transfer rate. Besides the above, a repeated transmission of the data may be required that may consequently impair real-time transmission of the information signal.
It is therefore an object of the present invention to provide improvements in a receiving apparatus and a transmitting/receiving system which are capable of realizing exact transmission and reception of information signals with stability and certainty.
According to one aspect of the present invention, there is provided a receiving apparatus for receiving a plurality of information signals having mutually different frequency bands modulated and sent from a transmitting apparatus via an electric power line. The receiving apparatus has a receiving means for selectively receiving the information signal of a unique frequency band out of the plural information signals having mutually different frequency bands transmitted via the power line; a transmission quality decision means for deciding the transmission quality of the information signal having the unique frequency band received selectively by the receiving means; and a switching control means for switching under control the information signal received by the receiving means in response to the result of the decision obtained from the transmission quality decision means.
According to another aspect of the present invention, there is provided a transmitting/receiving system consisting of a transmitting apparatus and a receiving apparatus. The transmitting apparatus comprises a transmitting means for sending a plurality of modulated information signals having mutually different frequency bands via an electric power line. The receiving apparatus comprises a receiving means for selectively receiving the information signal having a unique frequency band out of the plural information signals having mutually different frequency bands transmitted via the power line; a transmission quality decision means for deciding the transmission quality of the information signal of the unique frequency band received selectively by the receiving means; and a switching control means for switching under control the information signal received by the receiving means in response to the result of the decision obtained from the transmission quality decision means.
The above and other features and advantages of the present invention will become apparent from the following description which will be given with reference to the illustrative accompanying drawings.